On Mon, Jul 16, 2018 at 12:39 AM Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
4.17-stable review patch. If anyone has any objections, please let me know.
From: Marc Orr marcorr@google.com
commit 0447378a4a793da008451fad50bc0f93e9675ae6 upstream.
This patch extends the checks done prior to a nested VM entry. Specifically, it extends the check_vmentry_prereqs function with checks for fields relevant to the VM-entry event injection information, as described in the Intel SDM, volume 3.
This patch is motivated by a syzkaller bug, where a bad VM-entry interruption information field is generated in the VMCS02, which causes the nested VM launch to fail. Then, KVM fails to resume L1.
While KVM should be improved to correctly resume L1 execution after a failed nested launch, this change is justified because the existing code to resume L1 is flaky/ad-hoc and the test coverage for resuming L1 is sparse.
Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: Marc Orr marcorr@google.com [Removed comment whose parts were describing previous revisions and the rest was obvious from function/variable naming. - Radim] Signed-off-by: Radim Krčmář rkrcmar@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
arch/x86/include/asm/vmx.h | 3 ++ arch/x86/kvm/vmx.c | 67 +++++++++++++++++++++++++++++++++++++++++++++ arch/x86/kvm/x86.h | 9 ++++++ 3 files changed, 79 insertions(+)
--- a/arch/x86/include/asm/vmx.h +++ b/arch/x86/include/asm/vmx.h @@ -114,6 +114,7 @@ #define VMX_MISC_PREEMPTION_TIMER_RATE_MASK 0x0000001f #define VMX_MISC_SAVE_EFER_LMA 0x00000020 #define VMX_MISC_ACTIVITY_HLT 0x00000040 +#define VMX_MISC_ZERO_LEN_INS 0x40000000
/* VMFUNC functions */ #define VMX_VMFUNC_EPTP_SWITCHING 0x00000001 @@ -349,11 +350,13 @@ enum vmcs_field { #define VECTORING_INFO_VALID_MASK INTR_INFO_VALID_MASK
#define INTR_TYPE_EXT_INTR (0 << 8) /* external interrupt */ +#define INTR_TYPE_RESERVED (1 << 8) /* reserved */ #define INTR_TYPE_NMI_INTR (2 << 8) /* NMI */ #define INTR_TYPE_HARD_EXCEPTION (3 << 8) /* processor exception */ #define INTR_TYPE_SOFT_INTR (4 << 8) /* software interrupt */ #define INTR_TYPE_PRIV_SW_EXCEPTION (5 << 8) /* ICE breakpoint - undocumented */ #define INTR_TYPE_SOFT_EXCEPTION (6 << 8) /* software exception */ +#define INTR_TYPE_OTHER_EVENT (7 << 8) /* other event */
/* GUEST_INTERRUPTIBILITY_INFO flags. */ #define GUEST_INTR_STATE_STI 0x00000001 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -1510,6 +1510,17 @@ static inline unsigned nested_cpu_vmx_mi return vmx_misc_cr3_count(to_vmx(vcpu)->nested.msrs.misc_low); }
+static inline bool nested_cpu_has_zero_length_injection(struct kvm_vcpu *vcpu) +{
return to_vmx(vcpu)->nested.msrs.misc_low & VMX_MISC_ZERO_LEN_INS;+}
+static inline bool nested_cpu_supports_monitor_trap_flag(struct kvm_vcpu *vcpu) +{
return to_vmx(vcpu)->nested.msrs.procbased_ctls_high &CPU_BASED_MONITOR_TRAP_FLAG;+}
static inline bool nested_cpu_has(struct vmcs12 *vmcs12, u32 bit) { return vmcs12->cpu_based_vm_exec_control & bit; @@ -11364,6 +11375,62 @@ static int check_vmentry_prereqs(struct !nested_cr3_valid(vcpu, vmcs12->host_cr3)) return VMXERR_ENTRY_INVALID_HOST_STATE_FIELD;
/** From the Intel SDM, volume 3:* Fields relevant to VM-entry event injection must be set properly.* These fields are the VM-entry interruption-information field, the* VM-entry exception error code, and the VM-entry instruction length.*/if (vmcs12->vm_entry_intr_info_field & INTR_INFO_VALID_MASK) {u32 intr_info = vmcs12->vm_entry_intr_info_field;u8 vector = intr_info & INTR_INFO_VECTOR_MASK;u32 intr_type = intr_info & INTR_INFO_INTR_TYPE_MASK;bool has_error_code = intr_info & INTR_INFO_DELIVER_CODE_MASK;bool should_have_error_code;bool urg = nested_cpu_has2(vmcs12,SECONDARY_EXEC_UNRESTRICTED_GUEST);bool prot_mode = !urg || vmcs12->guest_cr0 & X86_CR0_PE;/* VM-entry interruption-info field: interruption type */if (intr_type == INTR_TYPE_RESERVED ||(intr_type == INTR_TYPE_OTHER_EVENT &&!nested_cpu_supports_monitor_trap_flag(vcpu)))return VMXERR_ENTRY_INVALID_CONTROL_FIELD;/* VM-entry interruption-info field: vector */if ((intr_type == INTR_TYPE_NMI_INTR && vector != NMI_VECTOR) ||(intr_type == INTR_TYPE_HARD_EXCEPTION && vector > 31) ||(intr_type == INTR_TYPE_OTHER_EVENT && vector != 0))return VMXERR_ENTRY_INVALID_CONTROL_FIELD;/* VM-entry interruption-info field: deliver error code */should_have_error_code =intr_type == INTR_TYPE_HARD_EXCEPTION && prot_mode &&x86_exception_has_error_code(vector);if (has_error_code != should_have_error_code)return VMXERR_ENTRY_INVALID_CONTROL_FIELD;/* VM-entry exception error code */if (has_error_code &&vmcs12->vm_entry_exception_error_code & GENMASK(31, 15))return VMXERR_ENTRY_INVALID_CONTROL_FIELD;/* VM-entry interruption-info field: reserved bits */if (intr_info & INTR_INFO_RESVD_BITS_MASK)return VMXERR_ENTRY_INVALID_CONTROL_FIELD;/* VM-entry instruction length */switch (intr_type) {case INTR_TYPE_SOFT_EXCEPTION:case INTR_TYPE_SOFT_INTR:case INTR_TYPE_PRIV_SW_EXCEPTION:if ((vmcs12->vm_entry_instruction_len > 15) ||(vmcs12->vm_entry_instruction_len == 0 &&!nested_cpu_has_zero_length_injection(vcpu)))return VMXERR_ENTRY_INVALID_CONTROL_FIELD;}}return 0;}
--- a/arch/x86/kvm/x86.h +++ b/arch/x86/kvm/x86.h @@ -110,6 +110,15 @@ static inline bool is_la57_mode(struct k #endif }
+static inline bool x86_exception_has_error_code(unsigned int vector) +{
static u32 exception_has_error_code = BIT(DF_VECTOR) | BIT(TS_VECTOR) |BIT(NP_VECTOR) | BIT(SS_VECTOR) | BIT(GP_VECTOR) |BIT(PF_VECTOR) | BIT(AC_VECTOR);return (1U << vector) & exception_has_error_code;+}
static inline bool mmu_is_nested(struct kvm_vcpu *vcpu) { return vcpu->arch.walk_mmu == &vcpu->arch.nested_mmu;
Reviewed-by: Marc Orr marcorr@google.com